What Is a Chord?
A chord is three or more notes sounding at the same time. That is the whole definition, and the rest of this page is you building one: count the half steps yourself, press the key you land on, and hear what arrives.
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A chord is three notes at the same time.
Why does one half step change the whole chord?
You counted four half steps up from a root and pressed the key you landed on. Then you counted seven and pressed that one. Three notes together is a triad, and it is the chord almost all western music is built from.
The middle one of those three is the third, and it is the only note in the chord carrying a mood. Four half steps up and the chord is major. Move that one key down to three and the root has not moved, the fifth has not moved, and the whole thing has gone dark.
Build C major in the block below and then press "Move the third down one". Play them back to back until you can hear which is which without looking.
The three notes and what each one does
The four ways to stack three notes
Same root every time. What changes is how far up you count. Play them back to back, then read why they feel the way they do.
Why it is called a third
On the keys you count half steps. On paper you count letter names, and that is where the word third comes from. Count it here.
Press a letter to hear it. Then count a third: start on a letter, count that one as number one, and stop at three.
Reading a chord symbol
- The letter is the root
C means count from C. That part never changes.
- Nothing after it means major
Plain C is the 4 and 7 you just built.
- A small m means minor
C to Cm is one note moving down one half step.
- A number means another note on top
C7, Cmaj7 and C9 all keep the triad and stack further. The name tells you what got added, not what got replaced.
Keep going
Everything in chords
- Half-Diminished Seventh Chord
- What Is a Chord?